The inventive concepts described herein relate to a semiconductor memory device, and more particularly, relate to an operating method of a non-volatile memory device and an operating method of a memory controller.
In general, a memory device may be volatile or non-volatile. A volatile memory device may lose data stored therein at power-off. A non-volatile memory device may retain data stored therein even at power-off. Examples of non-volatile memory devices include a read only memory (ROM), an electrically erasable programmable ROM (EEPROM), or the like.
A flash memory device introduced to be a flash EEPROM may be different from a conventional EEPROM in terms of their structures and operations. The flash memory device may perform an electric erase operation by a block unit and a program operation by a bit unit.
Threshold voltages of programmed memory cells in the flash memory device may vary due to various causes (e.g., floating gate coupling, charge loss with the lapse of time, etc.). A variation in threshold voltages of memory cells may reduce of the reliability of read data.